This invention is directed to a material that is extendible in all x/y plane directions.
A number of various material attributes are desirable for material used to make outer covers of absorbent articles. For example, in pant-like garments, machine direction extendibility is desirable because longitudinal conformability allows a crotch region of the garment to sag and bulge when loaded without pulling the waistband of the product down. Similarly, cross direction extendibility is desirable because lateral conformability maintains a snug, yet comfortable fit about a wearer""s hips. Furthermore, extendibility in all directions in the x/y plane contributes to an all-around form-fitting product.
Some materials, such as necked stretch-bonded laminates (NSBL), necked/creped spunbond attached to elastomerics, etc., have all-direction stretch, i.e., elongation with power recovery. These materials are relatively expensive because of the inclusion of relatively expensive elastomeric materials. However, high recovery forces are not always desirable in outer cover materials. Low recovery forces allow the garments to remain in a conforming shape on the wearer without exerting a considerable amount of retractive pressure and without restricting a wearer""s movements. Furthermore, when the garments are filled up by the wearer, low recovery forces allow the weight of the garment contents to pull the garment contents away from the wearer""s body without pulling the rest of the garment down on the wearer""s body, thereby maintaining close contact between the wearer and the garment in the waist area and around the leg openings to prevent leakage of any garment contents from the garment.
Breathability is a material attribute particularly desirable in absorbent articles. Breathable films and laminates typically block the passage of particulate matter, water and other liquids while allowing water vapor and/or air to pass through the material. Thus, breathable materials, when used in diapers or similar absorbent garments, reduce the relative humidity and temperature within the garment in comparison to such garments made of non-breathable films and laminates.
A liquid barrier is an inherently desirable material attribute of an absorbent article. The liquid barrier acts to prevent liquids from permeating through a surface of the garment and onto a wearer""s clothing or surroundings.
Various types of material with combined attributes are known in the art. For example, stretch-bonded laminates (SBL) deliver a machine direction extendible, breathable composite, but have no liquid barrier and little extendibility in a cross direction. More recent neck-bonded laminates deliver a cross direction extendible liquid barrier, but are not extendible in the machine direction. Other composites function as cloth-like, breathable barriers, but they have little or no extendibility in either a machine direction or a cross direction.
U.S. Pat. No. 5,114,781 issued to Morman on May 19, 1992, discloses a laminate that can extend in at least two directions. The laminate includes a reversibly necked nonwoven material and an elastic sheet.
U.S. Pat. No. 5,116,662 issued to Morman on May 26, 1992, discloses a laminate that can extend in at least two directions. The laminate includes a necked nonwoven material and an elastic sheet.
U.S. Pat. No. 5,883,028 issued to Morman, et al., on Mar. 16, 1999, discloses a laminate that can extend in at least two directions. The laminate is formed by attaching a nonwoven material that is necked in the cross direction to a water vapor-soluble elastomeric film that is stretched in the machine direction and has retraction in the machine direction.
There is a need or desire for a material that delivers a multitude of properties in a single composite, namely biaxial extendibility, low recovery force, breathability, liquid barrier properties, and is relatively inexpensive.
The present invention is directed to an extendible outer cover (EOC) material that can extend in all x/y plane directions. In one embodiment, the EOC is a laminate including a necked nonwoven web and a striated, breathable, microporous film having striated rugosities in the machine direction. The striated rugosities allow the film and the necked nonwoven web to extend in the cross direction. The material of this embodiment is made by stretching the filled film in the machine direction to cause breathability, laminating the stretched film to the nonwoven web, stretching the laminate in the machine direction to neck the nonwoven web and form the striations in the film, then creping the laminate to create machine direction extendibility. An elastomeric lamination and/or creping adhesive can be used to produce a laminate with minor retractive force.
In another embodiment of the invention, the EOC is a laminate including a single-layer cross-direction extendible film made from an extendible polymer that permits the film, along with a necked nonwoven web bonded to the film, to extend in the cross direction. The material of this embodiment is made by stretching the filled film in the machine direction to cause breathability, separately stretching a nonwoven web to cause necking, laminating the stretched film and the necked nonwoven web together, then creping the laminate to create machine direction extendibility. As in the previous embodiment, an elastomeric lamination and/or creping adhesive can be used to produce a laminate with minor retractive force.
The adhesive add-on level and bond pattern greatly affect material properties. Thus, the resulting material of the invention can have a high retractive force in one direction and low or no retractive force in another. Further retractive force can be imparted in one or both directions through the addition of elastomeric film, fibers, foams, scrims, or other elements.
With the foregoing in mind, it is a feature and advantage of the invention to provide a biaxially extendible, breathable laminate having liquid barrier properties and low recovery force.
It is also a feature and advantage of the invention to provide an improved biaxially extendible, breathable laminate useful in a wide variety of diaper outer covers, other personal care products, surgical gowns, and other breathable applications.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the examples and drawings.